Catheter introducer

ABSTRACT

An improved self-sealing gasket provides hemostasis while reducing the force required to move a catheter or guidewire positioned within the gasket. Slits formed on one surface of the gasket intersect with a central aperture formed on the opposite face of the gasket. An annular ring formed on the gasket assists in retaining the gasket within a catheter introducer. An annular shelf may be provided distally of the gasket to prevent dislodgement of the gasket if an instrument is inserted into the introducer off axially.

RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent applicationSer. No. 08/058,594, filed May 7, 1993.

FIELD OF THE INVENTION

This invention relates to improvements in vascular catheter introducersused in the introduction, manipulation and removal of catheters,guidewires and other instruments from a patient's vascular system inangiographic, angioplasty and other vascular procedures. The inventionrelates to introducers having an improved self-sealing gasket tomaintain hemostasis while reducing the resistance to movement of acatheter, guidewire or other instrument as it is passed through andmanipulated through the introducer.

Background of the Invention

A catheter introducer is a device that is placed, usuallypercutaneously, into a patient's body, such as into the vascular systemfor angiographic, angioplasty or other medical procedures. A catheterintroducer typically includes a tubular shaft that is insertable intothe patient's vascular system or other body region and a housingattached to the proximal end (the end disposed outside of the patient)of the tubular shaft. The housing contains and supports one or moreself-sealing hemostasis gaskets that close to prevent blood leakage whenno instrument is present in the introducer and to maintain a sealagainst and about such instrument to prevent blood loss while theinstrument is in place through the introducer.

In addition to providing a hemostasis seal, both when an instrument isor is not present in the introducer, it is important that the gasketpresents minimal drag and resistance to movement to the catheter,guidewire or other instrument in order to facilitate manipulation of theinstrument in the patient. The tactile response that the physiciansenses at the proximal end of the instrument is important to thephysician in order that he can feel obstructions or tortuous vascularanatomy as the instrument is advanced through that anatomy. Typically,hemostasis gaskets for catheter introducers have involved a compromisebetween maintaining an effective seal under all conditions of use andthe resistance to movement that the gasket imposes on a medicalinstrument.

Prior art devices have addressed the desirability of maintaining a sealwithout unduly impairing the ease of movement of the catheter throughthe gasket. Introducers may be made with self-sealing gaskets adapted toreceive and effect a seal only with instruments having a limited rangeof diameters. That typically has been less than satisfactory because itis common to require the use of a number of guidewires and cathetersthat must be inserted through the introducer having diameter ranges ofbetween about 0.035 inch to 0.118 inch or more. The self-sealinghemostasis gaskets disclosed in U.S. Pat. Nos. 4,000,739 (Stevens) and4,424,833 (Spector) are representative of prior art gaskets designed toreceive a specific size of instrument and adapted to accommodate arelatively limited range of instrument diameters.

U.S. Pat. No. 5,304,156 (Sylvanowicz) assigned to the assignee of thepresent invention discloses an improved catheter and guidewireintroducer that has a self-sealing gasket adapted to effect a seal bothin the presence and in the absence of a guidewire or catheter and wherethe range of diameters of guidewires and catheters that can be acceptedis substantially greater than the art that preceded it, including thedevices described in the Stevens and Specter patents. Moreover, thedevice described in the Sylvanowicz patent effected a seal over a widerange of devices while not significantly impairing the feel of thecatheter as it is manipulated through the introducer. Notwithstandingthe improvements achieved with the device described in the Sylvanowiczpatent, it would be desirable to further improve the device by furtherreducing the drag imposed on the catheter or the guidewire by the gasketwhile still maintaining an effective hemostasis seal. Additionally, itwould be desirable to enhance the manner in which the gasket is anchoredin the housing, particularly so that when relatively large diametercatheters are inserted through the gasket, the gasket is retainedsecurely in place in the housing and will resist any tendency for therelatively large diameter catheter to dislodge the gasket. It also isappreciated that instruments presented to the gasket off angle maydislodge the gasket from the housing, which could lead to a loss ofhemostasis. An introducer which prevents detachment of the gasket insuch situations would be desirable. It is among the objects of thepresent invention to provide such an improved introducer and gasket.

SUMMARY OF THE INVENTION

In one aspect of the invention, the gasket has a geometry similar tothat described in Sylvanowicz U.S. Pat. No. 5,304,156 and applicationSer. No. 08/058,594 but modified to provide still further improvementsby reducing the frictional drag between the catheter and the gasket incombination with optimized material characteristics for the gasket. Inparticular, the gasket is made substantially thinner than that describedin the Sylvanowicz patent and even thinner than that described inapplication Ser. No. 08/058,594. In another aspect of the invention, thegasket is modified to include improved anchoring means by which thegasket is more firmly secured in the housing. That is particularlydesirable with the thinned configuration gasket which, because of itsthin construction, might otherwise display an increased tendency to bedislodged when a large diameter catheter is inserted through the gasket.

It is among the objects of the present invention to provide a gasketthat can be utilized in a catheter introducer to provide increased easeof movement while maintaining hemostasis of a wide range of diameters ofcatheters and guidewires that can be passed through the gasket.

Another object of the invention is to provide a catheter introducerhaving a gasket that is thinner and provides improved materialcharacteristics over prior catheter introducer gaskets to allow improvedtactile response for the physician while maintaining hemostasis overextended periods of time.

Yet another object of the invention is to provide an improved catheterintroducer having a one-piece hemostasis gasket and an improved meansfor anchoring the gasket to resist its being dislodged when a largediameter catheter is inserted.

Still another object of the invention is to provide a annular retainingshelf within the housing which prevents dislodgement of the gasketduring insertion of medical instruments through the gasket whileallowing for limited deflection of the gasket.

A still further object of the invention is to provide an introducerwhich attempts to correct off angle introduction of an instrument and,additionally, which reduces the incidence of dislodgement of the gasketwhen the instrument is being inserted off-axially.

DESCRIPTION OF THE DRAWINGS

The foregoing and other objects and advantages of the invention will beappreciated more fully from the following further description thereof,with reference to the accompanying drawings wherein:

FIG. 1 is a schematic illustration of a housing of a catheter introducersectioned to illustrate the internal structure of the housing and thegasket contained therein;

FIG. 2 is a cross-sectional view of the gasket of the present invention.

FIG. 3 is another view of the gasket of the present inventionillustrating the slits as viewed from the surface of the gasketcontaining the central aperture.

FIG. 4 is an illustration of the gasket of the present invention mountedin the housing of the catheter introducer section to illustrate theinternal structure of the housing.

FIG. 5 illustrates the operation of the gasket of the present inventionwith a large diameter instrument inserted therethrough.

FIG. 6 illustrates the operation of the gasket of the present inventionwith a small diameter guidewire passed therethrough.

FIG. 7 illustrates another embodiment of the present invention with aretaining ring affixed to the gasket of FIGS. 2 and 3.

FIG. 8 illustrates yet another embodiment of the present invention inwhich a annular retaining shelf is formed within a catheter introducerhousing.

DESCRIPTION OF THE ILLUSTRATIVE EMBODIMENTS

FIG. 1 illustrates, in section, the proximal portion of a catheterintroducer 2 including a proximal housing 6 and a small portion of atubular sheath 4 that is attached to and extends distally from thehousing 6. The tubular sheath is intended to be inserted into apatient's blood vessel, typically in a percutaneous procedure.

The housing contains a self-sealing hemostasis gasket 8 having ageometry illustrated in FIGS. 2 and 3 and in the aforementioned U.S.Pat. No. 5,304,156 and application Ser. No. 08/058,594, the disclosuresof which are incorporated herein by reference in their entireties.

The gasket 8 is disk shaped and is captured between the housing 6 and anend cap 14 secured to the proximal end of the housing 6. The end cap 14is provided with an aperture 16 through which catheters and guidewiresmay be inserted through the gasket 8, the interior 18 of the housing andthe lumen 20 of the shaft 4. The cap 14 may be provided with acircumferential lip 21 that mates with a shoulder on the proximal end ofthe housing 6. Other configurations for attachment of the cap to thehousing may be provided. The end cap and housing may be joined by any ofa variety of gluing or welding techniques known to those skilled in theart for securing such plastic components together. The housing and endcap each have annular surfaces 22, 24 that face each other, whenassembled, and engage, respectively, the distal and proximal surfaces10, 12 of the gasket 8. In order to further secure the gasket 8 betweenthe housing and the end cap, each of the annular surfaces 22, 24 may beprovided with circumferential ridges 26, 28, adapted to securely pressinto the surfaces 10, 12 of the gasket 8.

The cap may be provided with an annular reservoir 30 to retain alubricant as described in application Ser. No. 08/058,594. The reservoirmay take the form of an annular slot 30 formed in the distal face of theend cap. The surface of the end cap that defines the aperture 16 servesas a lip 31 to partly define the reservoir 30. The distal edge of thelip normally contacts the proximal surface 12 of the gasket to retainthe lubricant but to permit it to be released when the gasket 8 isflexed upon insertion of a catheter. The functioning of the reservoir isdescribed more fully in application Ser. No. 08/058,594.

FIGS. 2 and 3 illustrate the gasket which is geometrically similar tothat disclosed in U.S. Pat. No. 5,304,156 and application Ser. No.08/058,594. The gasket 8 differs from the gaskets described in thepatent and application in several respects. The gasket 8 is thinner, ofthe order of 0.050 inch thickness. Additionally, central aperture 304 inthe proximal face of the gasket, although the same diameter as in theabove-referenced patent and application (0.029 inch) is not as deep,being of the order of 0.020 inch because the gasket 8 is substantiallythinner than that disclosed in the patent.

As noted above, a preferred total thickness of the gasket is 0.05 inch.The slits 306 have a depth of 0.036 inch. The central aperture has adepth of 0.020 inch, with the slits extending into the radial walls 308of the central aperture a distance of 0.006 inch. By extending the slitsthrough and into the walls 308 of the central aperture, the gasket isweakened about the central aperture so that it can yield to a relativelylarge diameter catheter that is forced through the central aperture,even when the catheter diameter is much greater than that of the centralaperture. Significantly, with the present invention, a relatively largecatheter can be advanced through the gasket but with even lessresistance and improved feel over the gasket configurations described inU.S. Pat. No. 5,304,156 and application Ser. No. 08/058,594.

Providing only partial slitting of the central aperture has theadditional advantage that guidewires, typically 0.035 to 0.038 inch indiameter, will also be sealed by the 0.029 inch diameter centralaperture. While the depth of the slits into one face of the gasket andthe depth of the central aperture into the opposite face of the gasketmay be varied, it is important that the slits extend a distance into theradial walls 308 which are formed by the central aperture. In thepreferred embodiment, the central aperture has a depth of 0.020 inchwhile the preferred slit depth is 0.036 inch.

In the preferred embodiment, the slits 306 preferably have a radiallength 310 of 0.030 inches, giving a total slit diameter of 0.060 inch.This radial diameter of the slits differs from the diameter given inU.S. Pat. No. 5,304,156 which has a longer radial diameter of 0.075 inchradial length and, thus, a total slit diameter of 0.150 inch. In thepresent invention, the slits can be made of a smaller radial diameterbecause of the relatively thinner thickness of the gasket. Were theslits to be made of a radial length the same or similar to that of thatdescribed in U.S. Pat. No. 5,304,156, the gasket might tend to leak bothin the presence of a guidewire or catheter in the gasket as well aswithout such an instrument through the gasket, due to blood pressure.Thus, the thinner gasket of the present invention provides thehemostasis ability of a thicker gasket but as well provides a relativeease of movement of catheters through the gasket.

An additional factor affecting both hemostasis and the "feel" and easeof movement of a guidewire or catheter through a gasket is theparticular material which is used for the construction of the gasket. Astiffer material, for example, while perhaps providing good hemostasis,may impede the ease of movement of instruments inserted through thegasket. We have found that in the gasket of the present invention thatcertain ranges of hardness of materials of the gasket, preferably anelastomeric silicone, perform better than others. The maximum functionalrange for the hemostasis gasket of the present invention is a hardnessof a durometer of 15 to 60 Shore A Durometer. A preferred range ofhardness is 32-45 Shore A Durometer with a more preferable range ofapproximately 37±5 Shore A Durometer with the material in each of thecases being preferably made of an elastomer material, such as siliconeand in the illustrative dimensions described herein. While the preferredthickness of the gasket has been given as 0.050 inches, it is understoodthat the ability of the present gasket to seal as well as to provideefficient "feel", the gasket may be made in a range from 0.040 inches to0.060 inches. The overall hemostasis as well as ease of movement and"feel" is affected in the gasket of the present invention by therelative sizes of the depth of the central aperture, the depth of theslits, the radial length of the slits and the hardness and type ofmaterial used to form the gasket.

Although the FIGS. 2 and 3 show 3 slits, it should be understood that agreater or lesser number may be utilized, as is known to those skilledin the art in order to achieve the particular desired characteristics ofthe gasket to best achieve the desired goals of maintenance ofhemostasis as well as ease of movement of catheters, guidewires andother instruments passed through the gasket.

The gasket 8, being relatively thin, lessens the amount of forcerequired for catheter movement compared with a similar, but thicker,gasket while maintaining hemostasis. It is somewhat common inangiography and angioplasty procedures for there to be an intervalbetween procedures after the catheter introducer has been placed in thepatient's vascular system. For example, the introducer may be placed ina patient's system to perform angiographic testing to locate anyobstruction in the patient's arteries. If such obstructions have beenfound, and an angioplasty procedure scheduled the next day, it isinconvenient to remove the catheter introducer and reinsert anotherintroducer the following day. Instead, the introducer is left in place.To prevent abrading of the surrounding vessel by the tip of theintroducer and to avoid kinking of the thin-walled sheath if thepatient's body shifts or moves, an obturator is placed in the catheter.In a catheter introducer having a gasket with a thickness less than0.050 inch, the extended use of the obturator may permanently deform thegasket, due to its thinness. The gasket will then be unable to maintainhemostasis during the subsequent angioplasty procedure. With a siliconeelastomer gasket as described, approximately 0.050 inch thick, theability to maintain hemostasis is retained despite the extended use ofan obturator.

FIG. 3 shows another view of the gasket 8 of FIG. 1 as seen from thesurface of the gasket in which the central aperture is formed. As can beseen in FIG. 3, the slits 306 are only through slits in the region 312bounded by and defined by the central aperture. That is, while slits arecut through a predetermined depth into the surface of the gasketopposite that of the central aperture, the regions between the slitsoutside the periphery of the aperture are not "freely moving" due to theone-piece construction of the gasket. The region 312 in which thecentral aperture and the flaps between the slits overlap is freelymovable. While the entire radial length of the slits does not freelymove, the depth of the slits cut into the surface of the gasket weakensthat surface allowing, in addition to the overlapping of the centralaperture and the slits, the gasket to give way when a large diametercatheter is inserted through the gasket while maintaining the ability toseal around small diameter guidewires as well as due to the presence ofthe small diameter central aperture.

FIG. 4 illustrates a housing 314 into which the gasket 8 of the presentinvention is inserted. The gasket 8 is fitted into a a circular recess316 within the housing 314. Tube 318 may be elongated and is designed tobe inserted into a patient's vascular system.

FIGS. 5 and 6 illustrate the operation of the gasket of the presentinvention with instruments of varying diameters passed therethrough.FIG. 5 illustrates the position of the gasket with a large diametercatheter or other instrument 400 passed through gasket 8. As can be seenin FIG. 5, the catheter is of a diameter much greater than the diameterof the central aperture 304 of FIG. 2. For example, the diameter of theaperture has been given as 0.029 inch, while a 8 French catheter whichmay be typically used with the gasket of the present invention, has adiameter of approximately 0.105 inch. The central aperture, uponinsertion of the catheter, stretches and opens, assisted by theweakening of the radial walls provided by the overlapping slits and theslitting of the inwardly facing surface to allow the passage of acatheter therethrough. The catheter is sealed by the gasket 8 tomaintain hemostasis. When the catheter is removed, the gasket returns tothe position as shown in FIGS. 2 and 3.

FIG. 6 illustrates the operation of the present gasket with a guide wireor small catheter 402 passed therethrough. Because the guidewire isslightly, but not greatly, larger in diameter than the central aperture304 shown in FIG. 2, the central aperture 304 stretches but is notdeflected significantly, and the slitted portion of the gasket 8 willmove out of the tube to allow the passage of the guidewire. When theguidewire is removed, the flaps formed by the slits return to theirnormal position shown in FIGS. 2 and 3.

FIG. 7 illustrates another embodiment of the gasket of the presentinvention. Gasket 400 is shown installed within a housing 402 of acatheter introducer such as is shown in FIGS. 1 or 4 of the presentinvention. Gasket 400 is identical or substantially similar to thegasket 8 illustrated in FIGS. 2 and 3 except that an annular distallyextending ring 404 is formed about the periphery of the face 406 of thegasket 400. The annular ring 404, which preferably is formed of the samematerial and in one-piece with the gasket 400 is received in an annularrecess 408 formed in the end wall 410 of the housing 402. An end cap 412is then assembled, by glue, welding or other well-known means, onto theend wall 410 to seal the housing 402 as well as to retain the gasket 400on the side of the gasket containing the central aperture. Circular ribs414, 418 are formed respectively in the end cap and in the housing 402to press into the relatively resilient material of the gasket 400 tohelp with its retention within the housing. When a large catheter ispassed through the end cap opening 422 into and through the gasket, dueto the large size of the catheter, there is an increased risk that thegasket may become dislodged from its retaining structure.

By extending the gasket by means of the annular ring 404 and capturingthe annular ring within an annular recess 408 as well as by fixing theperiphery of the outside surface of the gasket by means of the end cap,the fixation of the gasket within the housing 402 is assured anddislodgement of the gasket is prevented. In addition to providing anannular ring on the inside surface 406 of the gasket, it is possible toadditionally affix a similar ring on the outside surface (the surfacecontaining the central aperture) and providing a complementary annularrecess in the end cap 412 to provide even better retention of the gasket400 within the housing 402. Alternatively, the annular ring 404 may beformed only on the outer surface of the gasket which mates with anannular recess in end cap 412, to retain the gasket.

FIG. 8 illustrates a modified version of the catheter introducer housingof FIG. 1 which includes an annular retaining shelf to preventdislodgement of the gasket in the event that the physician attempts topush a medical instrument, such as an obturator, through the gasket at anon-axial angle (an insertion angle other than along the longitudinalaxis of the housing 6 and lumen 20 of FIG. 1). Such action tends todislodge the gasket from the grip of the circumferential ridges 26 and28 shown in the housing of FIG. 1. FIG. 8 illustrates a proximal housing500 which retains a gasket 502, which may be of the type illustrated inFIGS. 2 and 3. An end cap 504 is secured to the proximal end of thehousing 500. Catheters, guidewires, obturators and other medicalinstruments may be inserted through the aperture 506, the gasket 502,the interior 508 of the proximal housing and into the lumen 510 locateddistally of the proximal housing 500.

As shown in FIG. 8, the cap 504 may be provided with a lip 512 whichoverlies and mates with a shoulder 514 formed at the proximal end of thehousing 500. As described with respect to the housing of FIG. 1, variousconfigurations for attachment of the cap to the housing may be provided.The housing and the cap each have annular surfaces 516 and 518 that faceone another when assembled and engage respectively the distal andproximal surfaces 520 and 522 of the gasket 502. In order to furthersecure the gasket 502 between the housing and the end cap, each of theannular surfaces 516 and 518 may be provided with circumferential ridges524 and 526 which press into the surfaces 520 and 522. In addition, thehousing includes a annular protrusion or shelf 528 which extendsinwardly from the annular surface 516. The annular shelf 528 projectsinto the interior 508 to reduce the diameter of the hole to less thanthe diameter of the interior space 508. The annular shelf 528 ispreferably inclined at 532 in a distally facing angular direction on theside of the shelf which faces the surface 520 of the gasket.

The circumferential ridges 524 and 526 generally are sufficient toretain the gasket during axial insertion of guidewires, catheters andother medical instruments through the housing 500. However, if theseinstruments or a larger instrument such as a dilator is pushed throughthe aperture 506 and against the gasket at an angle rather than alongthe axis of the introducer (proper angle of insertion shown as arrow 600and off-axial insertion shown as arrow 602), the tip of the dilator maynot come into contact with the central aperture 530 of the gasket butrather with another portion of the surface 522. In that event, the tipof the dilator will not be pushing against the central aperture 530,which is designed to open to receive the dilator, but rather a surfacewhich has no opening(s). The result is that the gasket may be dislodgedfrom the circumferential ridges 524 and 526 retaining the gasket.Dislodgement of the gasket will cause a loss of hemostasis and potentialdangers to the patient and physician alike due to blood loss. Theannular shelf 528 solves the problem of gasket dislodgement by providingan abutting surface for the surface 520 of the gasket when the gasket isdeformed by the force of a dilator or other instrument pressing on theoutwardly facing surface 522 of the gasket. The annular shelf will notonly reduce the possibility of the gasket becoming dislodged from thehousing, but also tends to force the physician to center the tip of thedilator as the physician meets resistance in attempting to insert thedilator at an angle other than axially. In addition, even in an axialinsertion of a dilator or other instrument, the annular shelf assists inlimiting the amount of deflection of the gasket by abutment of theinwardly facing surface 520 of the gasket against the inclined surfaceof the shelf.

The annular shelf is preferably constructed with the inclined surface532 to allow for some distal expansion or deflection of material formingthe gasket, but having an outside limit for movement and deflection ofthe gasket well below the point of dislodgement. It has been found, fora housing having an interior diameter 534 of 0.200 inch, that an annularshelf preferably has an opening diameter 536 which may range from 0.140inch to 0.175 inch. The minimum for opening diameter 536 is limited tothe outside diameter of the largest catheter or other medical instrumentwhich is to be inserted through the gasket. It has been found that evenan annular shelf which reduces the inner bore diameter only by 0.010inch to 0.015 inch is effective in retaining the gasket within thehousing in the event of an attempted non-axial insertion of a medicalinstrument.

It should be understood that the foregoing description of the inventionis intended merely to be illustrative thereof and that othermodifications and embodiments may be apparent to those skilled in theart without departing from its spirit.

Having thus described the invention, what we desire to claim and secureby Letters Patent is:
 1. A gasket for use in a catheter introducerhaving a housing that contains the gasket, the gasket comprising:aself-sealing, one piece gasket having an inwardly facing surface, anoutwardly facing surface, and a central aperture formed in its outwardlyfacing surface, the aperture extending a predetermined depth into thegasket and being defined in part by a circumferential wall; a pluralityof slits formed in the inwardly facing surface of the gasket andextending radially from a central region, the slits having a depth suchthat they intersect the circumferential wall, the central region of theslits overlapping the central aperture and defining a plurality of flapsnormally closing the aperture; the central aperture and the slits beingdimensioned to enable the gasket to form a seal about a range ofdiameters of devices that includes guidewires and catheters; and anannular ring extending from and beyond the inner facing surface of thegasket, the ring being engageable by the housing to secure the gasket inthe introducer.
 2. A gasket for use in a catheter introducer having ahousing that contains the gasket, the gasket comprising:a self-sealing,one piece gasket having an inwardly facing surface, an outwardly facingsurface, a central aperture in its outwardly facing surface, theaperture extending a predetermined depth into the gasket and beingdefined in part by a circumferential wall; a plurality of slits formedin the inwardly facing surface of the gasket and extending radially froma central region, the slits having a depth such that they intersect thecircumferential wall, the central region of the slits overlapping thecentral aperture and defining a plurality of flaps normally closing theaperture; and an annular ring extending from at least one of theinwardly facing surface or the outwardly facing surface of the gasket,the ring being adapted to be engaged by the housing to secure tho gasketin the housing.
 3. The gasket as defined in claim 2 wherein the annularring extends inwardly beyond the inwardly facing surface of the gasket.4. The gasket as defined in claim 2 wherein the annular ring extendsoutwardly beyond the outwardly facing surface of the gasket.
 5. Thegasket as defined in claim 2 wherein the annular ring extends bothoutwardly and inwardly, respectively, from the outwardly facing surfaceand the inwardly facing surface.
 6. A gasket for use in a catheterintroducer having a housing that contains the gasket, the gasketcomprising:a self-sealing one piece gasket having an inwardly facingsurface and an outwardly facing surface; and an annular ring extendingfrom at least one of the inwardly facing surface or the outwardly facingsurface of the gasket, the ring being adapted to be engaged by thehousing to secure the gasket in the housing.
 7. The gasket as defined inclaim 6 wherein the annular ring extends from and beyond the inwardlyfacing surface of the gasket.
 8. The gasket as defined in claim 6wherein the annular ring extends from and beyond the outwardly facingsurface of the gasket.
 9. The gasket as defined in claim 6 wherein theannular ring extends both outwardly; and inwardly, respectively from theoutwardly facing surface and the inwardly facing surface.
 10. The gasketdefined in claim 6 wherein the gasket includes a central aperture in itsoutwardly facing surface, the aperture extending a predetermined depthinto the gasket and being defined in part by a circumferential wall. 11.The gasket defined in claim 10 further comprising:the gasket having acentral aperture formed in its outwardly facing surface, the apertureextending a predetermined depth into the gasket and being defined inpart by a circumferential wall; a plurality of slits formed in theinwardly facing surface of the gasket and extending radially from acentral region, the slits having a depth such that they intersect thecircumferential wall, the central region of the slits overlapping thecentral aperture and defining a plurality of flaps normally closing theaperture.
 12. A catheter introducer comprising:a housing having an innerbore, an outer bore proximal of and forming a juncture with the innerbore, a shoulder defined at the juncture of the inner bore and the outerbore, and an annular recess defined by the shoulder, the outer borebeing larger in diameter than the inner bore; a gasket having a diametercorresponding substantially to that of the outer bore, including aninwardly facing surface, an outwardly facing surface, and an annularring extending from and beyond the inwardly facing surface of the gasketfor cooperation with the annular recess in the shoulder; a cap supportedby the housing and contacting the outwardly facing surface of the gasketto secure the gasket in the housing.
 13. The catheter introducer ofclaim 12 further including a reservoir for containing lubricating fluidbeing formed by a space between the cap and the outwardly facing surfaceof the gasket to lubricate medical instruments inserted through thegasket.
 14. The catheter introducer of claim 12 wherein the cap furtherincludes a descending lip that defines an annular space for containinglubricant between the descending lip and the outwardly-facing surface ofthe gasket to lubricate medical instruments inserted through the gasket.15. A catheter introducer comprising:a housing having an inner bore, anouter bore proximal of and forming a juncture with the inner bore, and ashoulder defined at the juncture of the inner bore and the outer bore,the outer bore being larger in diameter than the inner bore; aself-sealing gasket having a diameter corresponding substantially tothat of the outer bore, including an inwardly facing surface contactingthe shoulder and an outwardly facing surface; an annular shelf formeddistally of the shoulder and extending into the inner bore, the annularshelf defining a space in the inner bore that reduces the diameter ofthe inner bore, the annular shelf providing an annular abutment surfaceto limit deformation of the gasket when an instrument is inserted intothe housing; and an end cap supported by the housing and contacting theoutwardly facing surface of the gasket to secure the gasket in thehousing.
 16. The catheter introducer of claim 15 wherein the annularshelf has an inclined surface in and inward direction to allow limiteddeformation of the gasket in the inward direction.
 17. The catheterintroducer of claim 15 further comprising a circumferential ridgeextending outwardly from the annular shoulder and contacting theinwardly-facing surface of the gasket to secure the gasket in thehousing.
 18. The catheter introducer of claim 17 further comprising acircumferential ridge extending inwardly from the end cap and contactingthe outwardly-facing surface of the gasket to secure the gasket in thehousing.
 19. The catheter introducer of claim 15 whereby the gasketincludes an annular ring extending from and beyond the inwardly facingsurface of the gasket, and the shoulder of the housing defines anannular recess, the annular ring cooperating with the annular recess tosecure the gasket in the housing.
 20. A gasket for use in a catheterintroducer comprising:a self-sealing one piece gasket having an inwardlyfacing surface, an outwardly facing surface, and a central aperture inits outwardly facing surface, the aperture extending a predetermineddepth into the gasket and terminating at a bottom wall; an annular ringextending from at least one of the inwardly facing surface or theoutwardly facing surface of the gasket; a plurality of slits formed inthe inwardly facing surface of the gasket and extending radially from acentral region, the slits having a depth such that they intersect thebottom wall, the central region of the slits intersecting the bottomwall and defining a plurality of flaps normally closing the aperture;the radius of the central aperture being substantially less than theradius defined by each of the slits to seal a range of diameters ofdevices that includes guidewires and catheters.